Brigade-size and larger-size forces often use mobile radar systems to detect and track incoming artillery and rocket fire to determine the point of origin for counter-battery fire. These mobile radar systems are typically trailer mounted and towed by a vehicle, such as a HUMVEE.
These mobile radar systems usually take the form of a planar array that is either mechanically or electronically steered. In mechanically-steered systems, the planar array is continuously physically rotated 360° by a drive system. This enables the mechanically-steered radar to scan a full 360° of azimuth. Electronically-steered arrays, on the other hand, do not actually move while in operation. Rather, a sequence of electromagnetic “beams” is rapidly electronically swept over a 90° area. To scan a full 360° , the electronically-steered planar array must be physically repositioned (three times to scan the remaining 270° in 90° sectors) or supplemented by three additional systems, each scanning a different 90° sector of azimuth. Some electronically-steered mobile radar sets, such as the AN/TPQ-36 Firefinder radar, include a drive system for providing a 360° sectoring mode. In this mode, a first 90° sector is briefly electronically scanned and then the array is automatically rotated to sequentially scan, in turn, the three remaining 90° sectors.
Planar radar arrays have certain drawbacks. In particular, they are required to withstand wind loads and ice. Furthermore, to the extent that the arrays are rotated, they must be stable against off-axis rotation and tipping moments, etc. For mechanically-steered arrays, the actuation and drive systems are complex and expensive. And, to the extent that the issue of wind loads and ice is addressed by a more robust mechanical design (e.g., increased weight, etc.), the load on the drive system is increased, thereby requiring more power and heavier drive-system components. Additionally, it is difficult to provide sufficient cooling efficiency for air-cooled radar systems. Also, EMI shielding can be problematic for planar arrays.
In an attempt to reduce the weight and thereby increase the functionality and mobility of mobile radars, lightweight composite structures are being developed for this application. But it is proving to be problematic to implement planar radar antenna arrays using composite materials. In particular, it is proving to be difficult to develop composites that are adequately stiff to withstand deflection (e.g., weight, wind loads, ice, etc.), yet have suitable damage tolerance.
As a consequence, there is a need for a new design for a mobile radar array that addresses the shortcomings of the prior art, such as the tradeoff between weight and robustness, issues pertaining to cooling, EMI shielding, transportation, and the complexity of the drive system.